Answer:
= 3.36 mm
Explanation:
From Ohm's law,
(Voltage = Current * Resistance)

The geometric definition of resistance is

where
is the resistivity of the material,
and
are the length and cross-sectional area, respectively.


Since the wire is assumed to have a circular cross-section, its area is given by
where
is the diameter.


Resistivity of copper =
. With these and other given values,



speed of tortoise is given as v1 = 0.14 m/s
speed of hare is given as v2 = 20*0.14 = 2.8 m/s
now let say the total length of the path is "d"
so the total time taken by the tortoise to cover this

now given that hare took rest for 1 min
so total time of run for hare is (t - 60)s
so the distance that hare covered is given by

now by above two equations



and the time t is given by


so part a)
t = 63 s
part b)
d = 8.82 m